This invention relates to method and apparatus for forming upper stops of a concealed type slide fastener by fusing a portion of fastener elements on the pair of right and left fastener stringers of the slide fastener.
Consealed type slide fasteners are produced generally by making a pair of right and left fastener stringers each comprising a fastener tape having a turn-up along one side to which a row of fastener elements are secured, interengaging these fastener stringers into a fastener chain, removing the fastener elements at a predetermined spacing to form spaces, threading a slider through a space onto the elements, then, first forming a bottom stop and thereafter forming upper stops, and finally cutting the chain at the space to complete a slide fastener of a predetermined length.
In such process for producing concealed type slide fasteners as noted above, the upper stops are formed in such a way that, in an effort to prevent the turn-up from sticking to the main portion of the fastener tape by the effect of melted synthetic resin, the turn-ups are straightened back and the fastener elements, auxiliary stock of upper stop material and the strightened turn-ups are altogether clamped between an ultrasonic horn and a die for fusing them by heat. This kind of process for forming upper stops is disclosed, for example, in Japanese Patent Public Disclosure No. 101204/1980. However, even in this process, the turn-ups of the fastener tapes are clamped between the ultrasonic horn and the die together with the elements and the auxiliary stock. Therefore, there are such drawbacks that the woven yarns of the turn-ups melt or the liquid of the melted elements and the auxiliary stock infiltrate into the turn-ups and the threads with which coils of the fastener elements are sewn to the fastener tapes, making the turn-ups and the sewing threads fragile and lessening the value of the products.